October 12, 2010

Yesterday we covered the dry adiabatic process. It is very rare that the adiabatic process stays 100% dry like the scenario we talked about. There is almost always some level of moisture in the air, and that changes the process fairly dramatically. The process still starts in the same way though, sun heats the atmosphere, heats the earth, and the earth radiates heat back into the air. The air absorbs the heat and warms, but here's where things change. Air that is moist or saturated with moisture will still rise, but it will cool(release latent heat) and expand less quickly than dry air. There isn't a constant for the cooling rate of moist air, the closest thing we can come to is ~6 degrees Celsius per 1000m. Again, that rate is subject to change. Also, there are some different things that happen to the air as it rises, cools and interacts with the air around it. Moist air will rise and cool until the temperature of the rising air reaches the dew point(temperature where the air is 100% saturated) and then the vapor in the air will begin to condense and form clouds. The stronger the current of warm air rising, the farther up the condensation will take place, hence you will start to see clouds that form in what looks like columns building upward. Eventually that rising/cooling/condensing air will reach a level where it matches the temperature of the air around it and stop rising. It is also possible, just like in the dry adiabatic process that the warm air will cool too quickly and start to sink back toward the ground until it reaches that stable temperature. There you have it, the moist or saturated adiabatic process is one of the ways to create clouds. This process is particularly evident in the summertime as we get more of the sun's direct rays and our part of the earth gets heated more intensely. There are still other scenario's where the adiabatic process can start as dry, but as the air lifts and cools it becomes moist(remember cool air holds less water vapor than warm air)and then the moist adiabatic rules start to take effect. The whole process is quite complicated, but it's neat to know how it works. Enjoy!

No comments:

Post a Comment

Current Northeast Radar

Accuweather / 15 min interval

Current Severe Weather Alerts

Unisys National Radar

2010 Bridgestone Winter Classic Weather Forecast

I looked at January weather statistics for Pittsburgh in recent years, as well as the climate forecasts for this year and came up with what I think will be a good forecast for January 1st.This year is the beginning of a La Nina climate cycle, which means average temperatures and slightly above average precipitation for the Pittsburgh area. I'm also taking into account the recent storm activity and the lake effect snows which have been really cranking over the last few weeks.

I'm going to call for high temperatures slightly below freezing, with a stiff wind from the NW (10-12mph). For the game, more clouds than sun, chance of some sort of frozen precipitation, 60%.

Come back in a few weeks and see if I'm right!

About Me

I'm thirty something, married, and am in the process of moving from Baltimore to Phoenix. I currently work in IT, but am transitioning to a telecom voice centered role. This blog is my way of sharing that experience.